Every year, the youngsters in the orchestra undergo auditions and training before touring around Asia over the summer.

"It was an unbelievable concept," says Pontzious. "Twenty-five years ago, Hong Kong was a British colony. Many Vietnamese people were trying to escape their country in small boats. Those that landed on Hong Kong's shores were kept in refugee camps and then many were later returned to Vietnam. Our first two Vietnamese members came from one of those camps."

Over the years the 71-year-old American conductor has brought together many young Asian musicians who otherwise would not have had the chance to perform alongside one another because of political considerations.

"It was almost impossible to think that you could have musicians from the mainland and Taiwan sitting down in the same orchestra," says Pontzious. "It was massively difficult and time-consuming to get hold of the visas or travel documents so the mainlanders could travel to Hong Kong and Taiwan and vice versa."

In 2008, Pontzious orchestrated an opportunity for young artists and musicians from North and South Korea to appear together in the same music event.

In May, the AYO was awarded the Nikkei Asia Prize for its cultural diplomacy and work in nurturing young musicians in the region. It was the first Hong Kong organisation to win the award since it was launched 20 years ago.

"What they said in Tokyo is that we're putting a twist on globalisation," says Pontzious. "The head of the Nikkei prize committee called us this 'amazing orchestra'."

To mark its 25th anniversary, AYO has a three-concert programme lined up. It will stage two featuring Steven Isserlis as solo cellist at City Hall, followed by a grand finale at the Hong Kong Coliseum on August 16 with Canto-pop star Alan Tam Wing-lun.

"We wanted to have an event to mark the 25th anniversary," says Pontzious. "If you're doing an event at the Hong Kong Coliseum then you really have to appeal to a broad segment of the community."

The theme of the celebration can be summed up in one work: Beethoven's Symphony No 9, "the Choral", which the AYO will perform on August 14. Famous for its setting of Friedrich Schiller's poem in its last movement, Pontzious says the piece is most appropriate for the occasion.

"It's very hard to believe that we have come this far," the conductor says. "When we started 25 years ago, I don't think anyone expected there would be a year two, let alone a year 25."

After the weekend concerts, the troupe will resume its tour around the region, stopping in Taiwan and then going on to Japan. The choral parts in the performances are sung by performers from the host city or country, underlining the mission to bring artists of different nationalities together.

"It is a leap of faith to really unite East Asia in this project," Pontzious says. "We'll probably have over 1,000 singers involved at the end of the day. That's really quite fun. I'm not so sure anyone could make the claim that they've done so many different performances with different choruses."

He adds that over the years AYO has evolved to become more of a "pre-professional orchestra", with older members ready to audition for the next level in their career.

Today, the concept behind the AYO has been adopted by other groups, such as the National Youth Orchestra of the United States (which was in the city recently to perform as part of this year's International Arts Carnival). With no plans of slowing down, Pontzious says if AYO can continue evolving, then he foresees a healthy future.

"I am very proud," says Pontzious. "The orchestra has always risen to the occasionand created great performances and memories for everyone."

Asian Youth Orchestra 25th Anniversary Concert, Aug 14 and 15, 8pm, City Hall Concert Hall, Central; Aug 16, 8pm, Hong Kong Coliseum, Hung Hom, HK$100-HK$350, Urbtix. Inquiries: 2866 1623